PNLIPRP1 hypermethylation in exocrine pancreas links type 2 diabetes and cholesterol metabolism.

We postulated that T2D predisposes to exocrine pancreatic diseases through (epi)genetic mechanisms. We explored the methylome (methylationEPIC arrays) of the exocrine pancreas of 141 donors, assessing the impact of T2D. Epigenome-wide association study (EWAS) for T2D identified a hypermethylation in an enhancer of the Pancreatic-Lipase-Related-Protein 1 (PNLIPRP1) gene, associated with decreased PNLIPRP1 expression. PNLIPRP1 null variants (in 191K participants of the UKbiobank) associated with elevated glycemia and LDL-cholesterol. Mendelian Randomisation using 2.5M SNP OmniArrays in 111 donors evidenced that T2D was causal of PNLIPRP1 hypermethylation, which was causal for LDL-cholesterol. Further AR42J rat exocrine cell studies demonstrated that Pnliprp1 knockdown induced acinar-to-ductal metaplasia, a known pre-pancreatic cancer state, and increased cholesterol levels, reversible with statin. This (epi)genetic study suggests a role for PNLIPRP1 in human metabolism and on exocrine pancreas function with potential implications for pancreatic diseases.

The expression of genes in top obesity-associated loci is enriched in insula and substantia nigra brain regions involved in addiction and reward.

BACKGROUND: Genome-wide association studies (GWAS) have identified more than 250 loci associated with body mass index (BMI) and obesity. However, post-GWAS functional genomic investigations have been inadequate for understanding how these genetic loci physiologically impact disease development. METHODS: We performed a PCR-free expression assay targeting genes located nearby the GWAS-identified SNPs associated with BMI/obesity in a large panel of human tissues. Furthermore, we analyzed several genetic risk scores (GRS) summing GWAS-identified alleles associated with increased BMI in 4236 individuals. RESULTS: We found that the expression of BMI/obesity susceptibility genes was strongly enriched in the brain, especially in the insula (p = 4.7 × 10-9) and substantia nigra (p = 6.8 × 10-7), which are two brain regions involved in addiction and reward. Inversely, we found that top obesity/BMI-associated loci, including FTO, showed the strongest gene expression enrichment in the two brain regions. CONCLUSIONS: Our data suggest for the first time that the susceptibility genes for common obesity may have an effect on eating addiction and reward behaviors through their high expression in substantia nigra and insula, i.e., a different pattern from monogenic obesity genes that act in the hypothalamus and cause hyperphagia. Further epidemiological studies with relevant food behavior phenotypes are necessary to confirm these findings.

Functional analysis of four LDLR 5'UTR and promoter variants in patients with familial hypercholesterolaemia.

Familial hypercholesterolaemia (FH) is an autosomal dominant inherited disease characterised by increased low-density lipoprotein cholesterol (LDL-C) levels. The functionality of four novel variants within the LDLR 5'UTR and promoter located at c.-13A>G, c.-101T>C, c.-121T>C and c.-215A>G was investigated using in silico and in vitro assays, and a systemic bioinformatics analysis of all 36 reported promoter variants are presented. Bioinformatic tools predicted that all four variants occurred in sites likely to bind transcription factors and that binding was altered by the variant allele. Luciferase assay was performed for all the variants. Compared with wild type, the c.-101T>C and c.-121T>C variants showed significantly lower mean (±SD) luciferase activity (64 ± 8 and 72 ± 8%, all P<0.001), suggesting that these variants are causal of the FH phenotype. No significant effect on gene expression was seen for the c.-13A>G or c.-215A>G variants (96 ± 15 and 100 ± 12%), suggesting these variants are not FH causing. Similar results were seen for the c.-101T>C and c.-121T>C variants in lipid-depleted serum. However, a significant reduction in luciferase activity was seen in the c.-215A>G variant in lipid-depleted serum. Electrophoretic-mobility shift assays identified allele-specific binding of liver (hepatoma) nuclear proteins to c.-121T>C and suggestive differential binding to c.-101T>C but no binding to c.-215A>G. These data highlight the importance of in vitro testing of reported LDLR promoter variants to establish their role in FH. The functional assays performed suggest that the c.-101T>C and c.-121T>C variants are pathogenic, whereas c.-13A>G variant is benign, and the status of c.-215A>G remains unclear.